Deformation Law of the Main Canal Bottom Plate under Coupling Effect of Main Canal Leakage and Shield Tunneling

When a shield tunnel passes under the main canal of the South-to-North Water Diversion Project, leakage at the bottom of the canal structure can lead to more severe hazards. Therefore, to study the disturbance deformation patterns under the coupling effects of bidirectional interactions, the FEFLOW software was used to simulate the influence range of groundwater seepage under different leakage conditions in the canal. The FLAC3D software was employed to establish a model of the canal-stratum-tunnel system, and numerical simulations of cooperative deformation under different construction conditions were conducted. The study shows that when the local leakage volume in the canal approaches or exceeds 100 m³/day, the planar influence range of the leakage exceeds 100 m. In the vertical direction, the stratum from the leakage center to the tunnel roof transitions from the vadose zone to the saturated zone, changing from an unsaturated to a saturated state. Comparing the simulation results of normal conditions with leakage conditions, the deformation curves at the canal bottom exhibit "W-shaped" and "V-shaped" patterns, respectively, with maximum settlements of 3.6 mm and 6.4 mm, and settlement trough widths of 27 m and 45 m. The results indicate that leakage at the canal bottom increases the depth of the settlement trough. This is because the leakage reduces the soil strength and alters the compression coefficient within the affected range, requiring greater deformation in the saturated soil layer to counteract stress changes.